I am actually experimenting with 95Hz at the moment. Seems to work just a little better than 85Hz in my setup.
As the survey only allows you to vote up to 85Hz, that is where I've cast my vote. However, 95Hz works best for me (8361A's with 7360A's). However, it is hugely room dependent and experimentation will show you clear distinctions. As the Genelec rep said to me: "experiment until you find the correct level for your situation and don't be afraid to experiment above the levels proffered by received wisdom." When it's right, full frequency response and amazing timbre will be conspicuous. Having said that, the spl matching does seem to make a difference - so, maybe link the correct sub to monitor or (as I am now doing) try four subs that provide the dynamic range that you're seeking. In my case, 2 x 7360A's driving 2 x Velodyne DD12's.
Oh yes, and there is absolutely no hint of directivity: that is, you cannot detect the subs' locations!